An ordered three-dimensional (3D) microstructure is an ordered 3D structure at the micrometer scale. Such a microstructure can be formed, for example, by using a stereolithography technique, which relies on a bottom-up, layer-by-layer approach. This process usually involves a platform (substrate) that is lowered into a photo-monomer (photopolymer) bath in discrete steps. At each step, a laser is scanned over the area of the photo-monomer that is to be cured (polymerized) for that particular layer. Once the layer is cured, the platform is lowered a specific amount (determined by the processing parameters and desired feature/surface resolution) and the process is repeated until the full 3D structure is created.
3D ordered polymer cellular structures have also been created using optical interference pattern techniques, also called holographic lithography; however, structures made using these techniques have an ordered structure at the nanometer scale and the structures are limited to the possible interference patterns, as described in Campbell et al., “Fabrication Of Photonic Crystals For The Visible Spectrum By Holographic Lithography,” NATURE, Vol. 404, Mar. 2, 2000, which is incorporated by reference herein in its entirety.
Another example of a cellular structure is disclosed in Jang et al., “3D Polymer Microframes That Exploit Length-Scale-Dependent Mechanical Behavior,” Advanced Materials, Vol. 18, Issue 16, August 2006, which is incorporated by reference herein in its entirety. Jang et al. discloses a use of holographic interference lithography (IL) to create a 3D polymer microframe. As described above, structures created using such a technique are limited to the possible interference patterns.
Another example of a cellular structure is disclosed in Sypeck et al., “Multifunctional Periodic Cellular Solids And The Method Of Making Same,” U.S. Patent Application Publication No. 2004/0154252, Aug. 12, 2004, which is incorporated by reference herein in its entirety. Sypeck et al. discloses bonding truss elements to each other by solid state, liquid phase, pressing or other methods at points of contact to form a cellular structure of highly repeatable cell geometry. However, the bonding approach is based on a layer-by-layer approach.
Another example of a cellular structure is disclosed in Wadley et al., “Method For Manufacture Of Periodic Cellular Structure And Resulting Periodic Cellular Structure,” U.S. Patent Application Publication No. 2005/0202206, Sep. 15, 2005, which is incorporated by reference herein in its entirety. Publication No. 2005/0202206 discloses a lightweight periodic cellular structure having a stacked array of hollow or solid structural elements that are bonded at their contact points in order to form a stacked lattice structure. Further arrays may be stacked onto the stacked lattice structure in order to form a periodic cellular structure of varying thickness and depth. However, bonding the structural elements at their contact points is also based on a layer-by-layer approach.
Another example of a cellular structure is disclosed in Wadley et al., “Method For Manufacture Of Cellular Materials And Structures For Blast And Impact Mitigation And Resulting Structure,” U.S. Patent Application No. 2005/0255289, Nov. 17, 2005, which is incorporated by reference herein in its entirety. Publication No. 2005/0255289 discloses a method of constructing a structure. The method includes bonding cellular housings together to form at least a first array. The method may include bonding multiple arrays together or in communication with one another. However, the bonding method is also based on a layer-by-layer approach.
Another example of a cellular structure is disclosed in Kooistra et al., “Methods For Manufacture Of Multilayered Multifunctional Truss Structures And Related Structures There From,” U.S. Patent Application No. 2006/0080835, Apr. 20, 2006, which is incorporated by reference herein in its entirety. Kooistra et al. discloses a multilayered truss core that may be created from a single planar preform. Once the desired preform is manufactured it is then deformed into a three-dimensional (3D) truss network. While this deformation approach bypasses the need to stack and join monolayer truss cores, it requires that the single planar preform first be manufactured and then be deformed. Moreover, a key to the deformation process is to ensure that the preform is in its ductile temperature regime.
As such, there continues to be a need for more simply manufactured open-cellular structures having an ordered microstructure.